There are optical disks as information recording media having a sector structure. Recently, as media come to have higher density and larger capacity, recording, reproduction, and editing of real-time data including audio data or video data are performed in more applications.
As one form of editing, there is an editing technique that is referred to as “post-record (after-record) editing.” Post-record editing is an editing technique in which data already having been recorded on an information recording medium is reproduced, and then the reproduced data is processed and recorded again onto the information recording medium. As an example of post-record editing, a usage is conceivable in which audio data or video data having been recorded is reproduced, undergoes a process of mixing the audio data with music such as background music or of superimposing a caption image onto the video data, and is recorded again onto the disk.
Hereinafter, as one example of conventional techniques, an example relating to conditions for recording and reproducing audio data and video data simultaneously in post-record editing will be described.
FIG. 2 is a diagram one-dimensionally showing a part of the arrangements of audio data recording areas and video data recording areas on a disk. In FIG. 2, 210, 212, 220, 222 and 240 denote audio data recording areas, and audio data sets A1, A2, Aj, Aj+1 and Ae are recorded respectively in these recording areas. Furthermore, 211, 213, 221, 223 and 241 denote video data recording areas, and video data sets V1, V2, Vj, Vj+1 and Ve are recorded respectively in these recording areas. The audio data recording areas and the video data recording areas are arranged alternately on the disk. For example, video that corresponds to audio of the audio data A1 is recorded as the video data V1, and in a similar manner, A2 and V2, Aj and Vj, Aj+1 and Vj+1, and Ae and Ve respectively correspond to each other. Furthermore, the same disk further is provided with areas into which audio data or video data can be recorded, separated from the above-described data. Of these, such audio data recording areas are shown in FIG. 2, and 250, 252, 260, 262 and 270 denote audio data recording areas serving as a separate area. Audio data sets that are recorded into these areas respectively are referred to as B1, B2, Bj, Bj+1 and Be. The video data recording area 241 and the audio data recording area 250 are on the same disk, but they are arranged apart from each other. It should be noted that there are a large number of pairs of an audio data recording area and a video data recording area before A1, between V2 and Aj, and between Vj+1 and Ae, although they are not shown. Similarly, there are a plurality of audio data recording areas between B2 and Bj, and between Bj+1 and Be in the separate area. Furthermore, there may be data of another kind between an audio data recording area and a video data recording area, or between a video data recording area and an audio data recording area, although it is not shown. The data of another kind will be described later with reference to FIG. 5.
A conventional example will be described in which post-record editing is performed on the thus arranged data in FIG. 2. In FIG. 2, a post-record starting point for audio is shown midway in the audio data A1, and a post-record starting point for video is shown midway in the video data V1, which corresponds to A1. In post-record editing, while video and audio are reproduced for confirmation, a post-record starting point is determined and post-record editing is started. Thus, post-record editing of the audio data A1 including the post-record editing points shown in FIG. 2 is started in a state where reproduction has been started from data slightly before A1. When post-record editing is started, not only are audio data and video data reproduced, but also video or audio is recorded simultaneously.
FIG. 3 is a diagram showing one example of conventional methods for performing post-record editing. The recording areas shown in FIG. 3 are the same as those described in FIG. 2. In the example of conventional post-record editing shown in FIG. 3, an example will be described in which once reproduced and processed audio data is recorded, without using a separate area on the disk, into an audio data recording area in which the data has been recorded. In this specification, post-record editing that reproduces data in a data recording area in which the data already has been recorded, processes the reproduced data, and then records the data again into the same recording area is referred to as “post-record editing in the same area.”
In FIG. 3, it is assumed that reproduction already has been started from data slightly before the audio data A1, and data up to the starting edge of A1 has been reproduced on the disk. A time necessary for reproducing A1 from the starting edge to the ending edge is referred to as TA. After A1 is reproduced, the starting edge of the video data V1 is accessed. In FIG. 3, an access time from the ending edge of A1 to the starting edge of V1 is referred to as Tfav, but when A1 and V1 are arranged continuously with no data interposed therebetween, Tfav can be regarded as 0 and ignored. Then, V1 starts to be reproduced. In FIG. 3, a time necessary for reproducing V1 from the starting edge to the ending edge is referred to as TcV1.
In the processes up to this point, A1 and V1 that have been read out from the disk are decoded in a predetermined manner, and output as actual audio and video. Furthermore, for post-record editing, it is necessary to process these audio and video to be encoded into a data format in which the data can be recorded again onto the disk. Therefore, some process time is necessary until data that is to be written back onto the disk in post-record editing is prepared. In FIG. 3, an example is shown in which, since post-record data that is to be written back onto the audio data A1 has not been prepared yet, because of this process time, at the time point when data up to the ending edge of the video data V1 has been read out from the disk, the starting edge of the next audio data A2 is accessed directly. In FIG. 3, an access time from the ending edge of V1 to the starting edge of A2 is referred to as Tfva, but when V1 and A2 are arranged continuously with no data interposed therebetween, Tfva can be regarded as 0 and ignored.
Subsequently, it is assumed that data up to the ending edge of the video data V2 has been read out in a similar manner, and the above-described post-record data that is to be written back onto A1 has been prepared by this time point. Then, in order to record the post-record data, access is performed from the ending edge of V2 to the starting edge of A1 on the disk. In FIG. 3, this access time is referred to as Tf(1). At that time, the disk device is switched from a reproducing operation to a recording operation. Generally, when disk devicees are switched between a reproducing operation and a recording operation, a predetermined switching process time is often necessary. Therefore, the access time Tf(1) refers to the longer one of the time for moving from the ending edge of V2 to the starting edge of A1 and the process time for switching from reproducing to recording. In a state where the starting edge of the audio data A1 has been reached and the switching process from reproducing to recording has been completed, the post-record data is recorded onto the audio data A1. In FIG. 3, a time necessary for this recording is referred to as TA. After data up to the ending edge of A1 is recorded, access is performed from the ending edge of the audio data A1 to the starting edge of the audio data A3 in order to reproduce the next data. In FIG. 3, this access time is referred to as Tf(1). At that time, a predetermined switching process time is necessary because the disk device is switched from a recording operation to a reproducing operation. Therefore, the access time Tf(1) refers to the longer one of the time for moving from the ending edge of A1 to the starting edge of A3 and the process time for switching from recording to reproducing.
Subsequently, the audio data A3 and the video data V3 are read out in a similar manner, and the post-record data that is to be written back onto their preceding A2 has been prepared by this time point, and thus the audio data A2 is accessed and recording is performed thereonto. Then, the starting edge of their next reproduction data is accessed, and these processes are repeated. In the conventional example, post-record editing is performed by repeating these processes.
The portion from the audio data recording area 220 to the video data recording area 223 in FIG. 3 shows one cycle of the repetitive processes in this conventional post-record editing. In one cycle of the conventional post-record editing, the audio data Aj+1 and the video data Vj+1 are reproduced, then their preceding audio data Aj is accessed, and post-record data is recorded thereonto, and again the operation goes back to their next reproduction data. In FIG. 3, the time for reproducing audio data is referred to as TA, the time for reproducing the video data Vj+1 as TcVj+1, and the access time as Tf(j). In order to carry out post-record editing, it is necessary to satisfy conditions for performing successive reproduction in this one cycle.
FIG. 9 is a diagram showing one example of conventional methods for performing post-record editing in a separate area. The recording areas shown in FIG. 9 are the same as those described in FIG. 2. In the example of conventional post-record editing shown in FIG. 9, post-record editing is performed using a separate area on the disk. In this specification, post-record editing that reproduces data in a data recording area into which the data already has been recorded, processes the reproduced data, and then records the data into a separate area that is apart from the reproduced data on the disk is referred to as “post-record editing in a separate area.”
There is a difference between the post-record editing in the separate area shown in FIG. 9 and the post-record editing in the same area shown in FIG. 3 with regard to the time for accessing an area into which post-record data is to be recorded. In the post-record editing in the same area shown in FIG. 3, an access time from the ending edge of the video data Vj+1 to the starting edge of the audio data Aj is referred to as Tf(j), and this is a short-distance access because the reproduced data and the recorded data are in the same area. On the other hand, in FIG. 9, an access time from the ending edge of the video data Vj+1 to the starting edge of the audio data recording area 260 is referred to as Tf, and this is a long-distance access because this separate area that is used in the post-recording is provided apart on the disk. In FIG. 9, a time necessary for recording post-record data Bj into the audio data recording area 260 serving as the separate area is referred to as TB, and TB can be regarded to have the same length of time as TA in the post-record editing in the same area shown in FIG. 3.
As described above, the only difference between the post-record editing in the same area and the post-record editing in the separate area is their times for accessing an area into which post-record recording is performed. Herein, both of the access times are referred to uniformly as Tf(j). In order to realize post-record editing, it is necessary to satisfy conditions for performing successive reproduction in one cycle of the repetitive processes in post-record editing.
In one cycle of post-record editing, when, with respect to the j-th video data Vj, the size of the video data is taken as YVj, the bit rate of the video data as VdVj, the time for reproducing the video data as TcVj, the time for recording or reproducing audio data as TA, the access time from the audio data to the video data as Tfav, the time for reading out one ECC block as Ts, the number of ECC blocks that are skipped in the video data as “a”, and the number of ECC blocks that are skipped in the audio data as “b”, in order to realize one cycle of post-record editing, it is necessary to satisfy(time for consuming the j-th video data)≧(time for processing one cycle), that is,YVj/VdVj≧TA+Tfav+TcV(j+1)+2×Tf(j)+TA+(a+2×b)×Ts. 
Aside from the above, as a technique relating to post-record editing on an optical disk, a technique has been disclosed in, for example, JP H11-259992A (FIG. 3) in which original AV data is recorded while reserving an area for post-record editing in advance. It should be noted that there is no reference to a condition for realizing post-record editing in JP H11-259992A.
However, in the conventional method as shown in FIG. 3, it is necessary to perform access every time when one set of post-record data is recorded in one cycle of the repetitive processes in post-record editing, and thus there is the problem that conditions for realizing post-record editing become strict. When using this conventional method and determining as to the conditions for realizing post-record editing, it is often determined that post-record editing cannot be performed on a disk on which video and audio are recorded.